Axial flux electric machine

Abstract

The invention relates to an axial flux electric machine (1) comprising: - a stator (3) comprising a yoke (4), teeth (44) and stator windings (8) wound around the teeth (44); - a casing (2_2) housing the stator (3), wherein the yoke (4) is rigidly attached to a wall (20) of the casing (2_2); - a circular bus (7) to which ends (80) of the stator windings (8) are connected, wherein the circular bus (7) is arranged between the stator windings (8), wherein the yoke (4) comprises passages (42) on the side of the casing (2_1, 2_2) that pass radially through it, and wherein electrical connections (32, 34, 36) pass through the passages (42) in order to connect the circular bus (7) to phase terminals (94, 96) at the periphery of the electric machine (1).

Description

[0001] DESCRIPTION

[0002] Title of the invention: Axial flux electric machine

[0003] The present invention relates to the fields of electrical engineering and mechanics and more specifically concerns an axial flux electric machine.

[0004] Currently, electric or hybrid electric vehicles use electric traction or propulsion motors, which are often radial flux electric machines, that is to say that the stator windings of such a machine generate a magnetic flux in a radial direction relative to an axial direction corresponding to the axis of rotation of the machine.

[0005] In order to reduce the size of such a motor used for traction or propulsion of an electric vehicle, it is envisaged to use, instead of a radial flux electric machine, an axial flux electric machine. This type of machine is in fact generally more compact at least in one axial direction corresponding to the axis of rotation of the machine, which gives it a discoid appearance.

[0006] Such a machine therefore comprises a casing of overall cylindrical shape housing at least one stator comprising stator coils, and a rotor fixed to a rotating shaft passing through the casing in its middle. The stator coils are fixed in the casing between an internal cylindrical wall delimiting a bearing support for the rotating shaft, and an external cylindrical wall. These stator coils are arranged angularly all around the internal cylindrical wall, opposite the magnetic poles of the rotor.

[0007] To electrically connect the stator coils to the machine's phase terminals, intended to be connected to an inverter, the ends of a stator winding of each stator coil are first welded to a circular bus, for example a three-phase bus, arranged between the stator coils and one of the internal or external cylindrical walls of the casing. Then phases of the circular bus are connected to electrical connections linking the circular bus to the machine's phase terminals, accessible from outside the casing.

[0008] When the circular bus is arranged between the stator coils and the outer cylindrical wall, these electrical connections pass through, for example, the outer cylindrical wall of the housing. This configuration of the circular bus is advantageous for connecting the electrical machine to an inverter, but is radially bulky and is expensive in copper due to the dimensions of the circular bus.

[0009] When the circular bus is arranged between the stator coils and the internal cylindrical wall, the electrical connections connecting the circular bus to the phase terminals generally pass through a flat wall of the housing through which the rotating shaft exits. This solution adds axial space. In addition, it prevents the housing of another device, for example a gearbox, from being pressed directly against the flat wall of the electrical machine housing.

[0010] The present invention aims to remedy at least in part the aforementioned drawbacks by providing an axial flux electric machine and an electric or hybrid electric vehicle, which limit the radial and axial size of the electric machine despite the use of a circular bus arranged between stator coils of the machine and a rotating shaft secured to a rotor of the electric machine.

[0011] To this end, the invention proposes an axial flux electric machine, comprising:

[0012] - a rotor,

[0013] - a stator comprising a yoke, teeth projecting from the yoke towards the rotor, and stator windings wound around the teeth, the yoke having a crown shape extending radially from an inner radial periphery of the yoke to an outer radial periphery of the yoke,

[0014] - a casing housing the stator, the cylinder head being secured to a wall of the casing,

[0015] - a circular bus to which ends of the stator windings are connected, the circular bus being arranged radially on the side of the internal radial periphery of the yoke, the electrical machine being characterized in that the yoke comprises, on the side of the casing, passages passing radially through the yoke and extending from the internal radial periphery of the yoke to the external radial periphery of the yoke, and in that the electrical machine further comprises electrical connections capable of electrically connecting phase connections of the circular bus to phase terminals located in an external peripheral portion of the electrical machine, the electrical connections passing at least partly in the passages passing radially through the yoke.

[0016] Thanks to the invention, the electrical connections do not require an axial increase in the dimension of the electrical machine, since they can be entirely integrated into the thickness of the yoke. The latter is preferably fixed to a wall of the casing on the side opposite the teeth, which is a generally flat wall, by gluing, welding, or by a system of keys. There is no play between the wall of the casing and the yoke because the axial position of the stator is guaranteed by the casing. In addition, the radial dimension of the machine is limited, the circular bus being arranged between the stator windings and a passage made in the stator to allow a rotating shaft secured to the rotor to pass through.

[0017] It should be noted that by circular bus is meant here circular connection means, comprising several conductive rings (circular conductive bars) not necessarily closed, each conductive ring being capable of conducting a phase current associated with a part of the stator coils to which it is connected. One of the circular rings may correspond to a neutral connection of the electrical machine, not necessarily requiring access from outside the electrical machine (therefore not necessarily connected by an electrical connection to a dedicated terminal in the external peripheral portion of the machine).

[0018] Furthermore, in this application, an axial orientation or direction refers to the direction of the rotating shaft integral with the rotor, i.e., a direction parallel to the axis of this rotating shaft. A radial orientation or direction is orthogonal to the axial direction and secant to the axis of the rotating shaft. An angular orientation or direction is orthogonal to the axial direction and to the radial direction, i.e., is ortho-radial.

[0019] The axial flux electric machine according to the invention comprises, for example, a rotor and two stators, or more rotors and fewer or more stators. It has a discoid shape, i.e. its casing has a generally cylindrical shape that is compact in the axial direction. The bases of this generally cylindrical shape are, for example, traversed by the rotating shaft secured to the rotor. Alternatively, this rotating shaft only passes through one of these bases.

[0020] According to an optional feature of the invention, the electrical connections are covered with an electrically insulating material at least on portions thereof in the passages radially passing through the yoke. Such insulating protection is necessary when the wall of the casing and the yoke are metallic and not covered with electrically insulating material at the electrical connections. The casing is in fact generally made of aluminum and the yoke generally made of magnetic steel. The electrical connections preferably each connect a separate phase connection of the circular bus to a separate phase terminal located in the external peripheral portion of the electrical machine, passing through separate passages radially passing through the yoke.Using a separate passage per phase of the electric machine allows the electrical connections to be thick enough to carry a large current, while having passages in the yoke of reduced dimensions, which do not disturb the flow of the magnetic flux during operation of the electric machine.

[0021] Preferably in the invention, the passages radially passing through the yoke each have a common ortho-radial plane of symmetry with a tooth of the stator or each have an ortho-radial plane of symmetry located angularly at the level of a tooth of the stator, the distance between the passage and a winding notch adjacent to the tooth being greater than or equal to a thickness of the yoke. This characteristic makes it possible to hollow out the yoke at the base of the teeth in locations practically not crossed by the magnetic flux during operation of the electrical machine, and therefore not to disturb it.

[0022] In one embodiment of the invention, one of the phase terminals and one of the phase connections of the circular bus intersect the ortho-radial plane of symmetry, one of the electrical connections connecting said phase terminal to said phase connection following the ortho-radial plane of symmetry. This electrical connection having no deviation from the ortho-radial plane of symmetry, it is as short as possible which saves space and material while facilitating its assembly.

[0023] The electrical machine is for example three-phase, a first phase terminal and a first phase connection located on a first side of the ortho-radial plane of symmetry being connected by a first electrical connection via a passage radially passing through the yoke, located on the first side, a second phase terminal, a second phase connection and a second electrical connection corresponding to those which intersect or follow the ortho-radial plane of symmetry, a third phase terminal and a third phase connection located on a second side of the ortho-radial plane of symmetry opposite the first side, being connected by a third electrical connection via a passage radially passing through the yoke, located on the second side. This configuration further optimizes the size of the electrical connections and facilitates their assembly.The first and third electrical connections are, for example, symmetrical to each other with respect to the ortho-radial plane of symmetry and have only two ortho-radial bends.

[0024] Preferably in the invention, the passages radially passing through the yoke are radial grooves formed on a surface of the yoke opposite the wall of the casing. This embodiment facilitates the assembly of the electrical connections. In addition, when the radial grooves each have a common ortho-radial plane of symmetry with a tooth of the stator, they minimize the disturbance of the magnetic flux by each being centered on the edge of a tooth base. Alternatively, the passages are in the form of radial holes in the yoke, therefore at the base of the teeth.

[0025] According to an optional feature of this embodiment of the invention, the yoke comprises a radial groove per tooth of the stator, the electrical connections leaving a radial groove free between them, the phase terminals being grouped at an external periphery of the same tooth. These radial grooves make it possible to save material in the yoke without disturbing the magnetic flux passing through it during operation. They also make it easier to mount the yoke on the wall of the casing, when this yoke is segmented into different parts each comprising a stator tooth. Indeed, the radial grooves are used, for example, to position and / or angularly fix one segment out of two of the yoke on the wall of the casing, by sliding in keys of complementary shape, for example made of the same material as the wall of the casing.The radial grooves, for example, have a dovetail section to facilitate good angular and axial support of the cylinder head segments. Other shapes of the groove section are possible, for example rectangular.

[0026] Furthermore, the phase terminals of the electrical machine are, for example, grouped in a terminal block arranged on the radial periphery of one of the teeth, which facilitates electrical connections between the electrical machine and one or more inverters.

[0027] According to another optional feature of the invention, the circular bus comprises a conductive bar per phase, the conductive bars being connected to the ends of the stator windings by forks arranged angularly on these conductive bars, all of the conductive bars being overmolded while leaving free the phase connections connected to the electrical connections. This feature makes it easier to make the connections of the ends of the windings to the circular bus. The mechanical strength of the conductive bars between them is ensured by the overmolding. The phase connections of the circular bus are for example non-overmolded zones allowing each electrical connection to be welded by one of their ends, on one of these zones, each zone being located on a separate conductive bar of the circular bus.

[0028] Preferably, the electrical machine according to the invention comprises two stators and two corresponding circular buses, the electrical connections of each stator being electrically connected to each other in a terminal block comprising said phase terminals, in the external peripheral portion of the electrical machine, located in a radial extension of the casing of the electrical machine. The casing of the electrical machine is for example made in two parts, each forming a half-casing each housing one of the stators of the machine. The rotor being mounted between the two stators, the two half-casings are screwed to each other on the periphery of the rotor at the end of assembly of the electrical machine. The terminal block is for example integrated in a radial extension of one of the half-casings, forming a housing that the other of the half-casings closes axially.

[0029] The invention also relates to an electric or hybrid electric vehicle, comprising an electric machine according to the invention. The electric or hybrid electric vehicle according to the invention has advantages similar to those of the axial flux electric machine according to the invention.

[0030] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0031] [fig 1] represents a perspective view of an electrical machine according to the invention, in one embodiment of the invention, and in which one half of the casing is not shown to reveal a face of one of the stators of the electrical machine, intended to be fixed to this half of the casing,

[0032] [fig 2] represents in axial section a part of the electric machine of figure 1,

[0033] [fig 3] represents a stator tooth of a stator of an electric machine according to the invention, in an alternative embodiment of the invention, the tooth being wound and projecting from a yoke segment through which an electrical connection is arranged, and [fig 4] is an ortho-radial sectional view of a yoke segment of an electric machine according to the invention, from which a stator tooth projects, in another alternative embodiment of the invention.

[0034] According to an embodiment of the invention shown in Figure 1, an axial flux electrical machine 1 according to the invention comprises two stators 3 and a rotor 5, the rotor 5 being able to be secured to a rotating shaft of rotation axis X by means of a hub 54. The electrical machine 1 is three-phase, but as a variant it contains more or less than three supply phases.

[0035] The electrical machine 1 of generally discoid shape comprises a first casing 2_1 (referenced in figure 2) and a second casing 2_2 each housing one of the stators 3 of the electrical machine. The two casings 2_1 and 2_2 are screwed onto each other so as to form a complete casing or housing of the electrical machine 1, closing around the rotor 5 mounted between the stators 3. The casings 2_1 and 2_2 each comprise an external cylindrical wall on which screw passages are formed for fixing the casings 2_1 and 2_2 together, and a generally flat wall 20 (visible in figure 2) comprising a central hole capable of allowing the passage of the rotating shaft. The flat walls 20 of the casings 2_1 and 2_2 each comprise a bearing upright bordering this central hole and in which is mounted a bearing receiving the rotating shaft.

[0036] The stators 3 in each of the housings 2_1 and 2_2 are almost structurally identical, being symmetrical to each other with respect to a main extension plane of the rotor, and therefore comprise many identical components, referenced identically in the figures.

[0037] In particular, each stator 3 comprises a yoke 4, made for example of magnetic steel, stator teeth 44 (one being visible in Figure 2) projecting axially from the yoke 4, in the direction of the rotor 5. The stator teeth 44 are attached to the yoke 4 or are formed at the same time as the yoke 5, the latter possibly being a yoke formed from an assembly of magnetic sheets glued to each other, or from an assembly of magnetic steel segments, each segment comprising for example a stator tooth 44 attached or made of the same material as the segment, or the yoke 4 is formed from a block with the stator teeth 44. When the stator teeth 44 are attached to the yoke 4, the latter is possibly formed from a wound magnetic sheet.It is understood here that the yoke 4 is a base surmounted by the stator teeth 44, thus forming the bases of these, and intended to allow the magnetic flux to loop back inside the yoke 4 during operation of the electrical machine 1.

[0038] The cylinder head 4 takes the overall shape of a crown extending radially from an internal radial periphery 46 of the cylinder head 4 to an external radial periphery 48 of the cylinder head 4. The face 41 of the cylinder head 4 shown in FIG. 1, extending in an orthoradial plane, is fixed to the flat wall 20 of the casing 2_1, 2_2.

[0039] In this embodiment of the invention, the yoke 4 is segmented according to the different stator teeth 44, and has under the base of each stator tooth, on the face 41, a radial groove 42 extending from the internal radial periphery 46 of the yoke 4 to an external radial periphery 48 of the yoke 4. These radial grooves 42 are used when fixing the yoke to the flat wall 20, in particular to position the segments of the yoke 4. The corresponding positioning and / or fixing system uses for example a system of keys with a section of shape complementary to that of the sections of the radial grooves 42. The segments once positioned are for example screwed to the flat wall 20.

[0040] Stator windings 8 are wound around the stator teeth 44. To facilitate the mounting of these stator windings 8 on the stator teeth 44, an insulating winding support 82, shown in FIG. 2, on which a stator winding 8 is pre-wound, is fitted onto each stator tooth 44.

[0041] The ends 80 of the stator windings 8 are connected to a circular bus 7, formed of four conductive bars 71, 73, 75, and 77, and located radially within the limits of the internal radial periphery 46 of the yoke 4, that is to say that the circular bus 7 is closer to the rotating shaft than this internal radial periphery 46 of the yoke 4. These conductive bars are circular, forming rings nested radially within each other. Alternatively, these rings are not closed or are arranged differently.

[0042] In this embodiment of the invention, each conductive bar 71, 73, 75, and 77 comprises forks 78 angularly distributed on these bars and each allowing one end of one of the stator windings 8 to be welded thereto, thus electrically connecting the end of the stator winding 8 to one of the conductive bars 71, 73, 75, and 77. The forks are metallic and for example made of material or welded to the conductive bars 71, 73, 75, and 77. The material used for the forks and the conductive bars is preferably copper but other conductive materials are of course usable.

[0043] The conductive bar 71 corresponds for example to a neutral connection of the electrical machine 1, and the conductive bars 73, 75, and 77 carry the electrical phases of the electrical machine 1.

[0044] In order to ensure the mechanical strength of the circular bus 7 and in particular of the conductive bars to each other, it is partially overmolded. The corresponding overmolding 70 is visible in Figure 2. In particular in this Figure 2, an axial extension of the conductive bar 77 in the direction of the wall 20 of the casing, located angularly, is not overmolded to allow its connection by welding to an electrical connection 34. This axial extension thus forms a phase connection 74.

[0045] The circular bus 7 leaves an opening in its center capable of allowing the rotating shaft of the machine to pass through. As seen in Figure 2, the hub 54 of the rotor finds a space radially between the stator windings 8, so as to leave an axial air gap of the order of a millimeter between the rotor 5 and the stator 3.

[0046] The rotor 5 is formed of magnet poles 58 distributed angularly around the rotating shaft, these magnet poles 58 being inserted between branches of a composite body fixed centrally to the hub 54, a hoop 52 enclosing the magnet poles 58 at the periphery of the rotor 5 to counter the centrifugal forces on these magnet poles 58 during operation of the electrical machine 1.

[0047] Returning to Figure 1, the cylindrical wall of the second casing 2_2 comprises a radial extension housing a terminal block, in an external peripheral portion 9 of the electrical machine 1. The terminal block comprises three phase terminals 92, 94, 96 corresponding to the power supply phases of the electrical machine 1, and making it possible to electrically connect these three phase terminals 92, 94, 96 to one or more inverters. The phase terminals 92, 94, 96 each take, for example, the form of an eyelet connector for the passage of a fixing screw.

[0048] The terminal block is located radially at the outer periphery of one of the stator teeth 44, in particular it extends angularly only over a limited portion of the electrical machine 1, the outer peripheral portion 9 radially covering no more than two stator teeth 44. For each of the supply phases of the electrical machine 1, an electrical connection 32, 34, or 36 electrically connects one of the phase terminals respectively 92, 94, 96 to a respective phase connection 72, 74, 76 of the circular bus 7. These phase connections 72, 74, 76 correspond for example each to a location on a conductive bar of the circular bus 7, making it possible to weld the corresponding electrical connection 32, 34, 36 to this location. Of course, other types of connections can be used, for example by screwing.

[0049] The electrical connections 32, 34, or 36 here take the form of copper conductive bars covered, except at their ends, with an electrically insulating material. Alternatively, these conductive bars are each formed of conductive strands or a conductive wire of round section, made of copper or a different metallic material.

[0050] According to the invention, the conductive connections 32, 34, and 36 pass at least partly in passages passing radially through the yoke 4, that is to say, in this embodiment of the invention, in the radial grooves 42.

[0051] The conductive connections 32, 34, and 36 thus have no or very little additional axial bulk, the face 41 of the cylinder head 4 coming into contact with the flat wall 20 of the casing when it is fixed there.

[0052] They preferably leave, after this fixing, no play between on the one hand the flat wall 20 of the casing 2_1, 2_2 and on the other hand the flat surface of the face 41 on which the radial grooves 42 are hollowed. In the latter case, the conductive connections 32, 34, and 36 cannot protrude slightly axially from the radial grooves 42.

[0053] In Figures 3 and 4, an axial overflow of the conductive connections, relative to the flat surface of the face 41 on which the radial grooves 42 are hollowed, is permitted by the presence of ribs 43 projecting from the face 41 of the yoke 42, these ribs 43 being in contact with the flat wall 20 of the casing 2_1, 2_2 when the electrical machine 1 is assembled.

[0054] In this embodiment of the invention, the radial grooves 42 have a dovetail-shaped section, but other sections are of course conceivable.

[0055] In addition, the radial grooves 42 each intersect an ortho-radial plane of symmetry of a stator tooth 44, i.e. a plane passing through the X axis of the rotating shaft and separating the stator tooth 44 into two equal parts. The intersection of this ortho-radial plane of symmetry with the corresponding radial groove 42 is centered in the radial groove 42.

[0056] Figure 3 illustrates such an ortho-radial plane of symmetry P passing through a stator tooth 44, in an alternative embodiment of the invention. In this figure 3, the elements identical to those of figures 1 and 2 are referenced in the same way. In particular, the stator tooth 44 is provided with a stator winding 8 pre-wound on a winding support 82.

[0057] In this variant embodiment of the invention, the electrical connection 34 is partly inserted into the radial groove 42 arranged in the face 41 of the cylinder head 4 opposite the flat wall 20 of the casing.

[0058] This electrical connection 34 comprises an electrically insulating overmolding surrounding its conductive part except at its ends. This insulating overmolding extends angularly beyond the groove 42, in the axial clearance existing between the face 41 of the cylinder head 4 and the flat wall 20 of the casing 2_1, 2_2. This angular extension of the overmolding is assembled at the same time as the electrical connection 34 on the cylinder head 4, the electrical connections 32, 34, and 36 being first assembled on the cylinder head 4 and welded to the circular bus 7 before assembly of the whole on the casing 2_1, 2_2.

[0059] One of the ends of the electrical connection 34, intended to be fixed to the phase terminal 94, takes the form of an eyelet capable of receiving a fixing screw, while the other end of the electrical connection 34 is curved so as to offer a sufficient welding surface with the corresponding conductive bar of the circular bus 7.

[0060] In another variant embodiment visible in Figure 4, in which the elements identical to those of Figures 1, 2 and 3 are referenced in the same way, the tooth 44 has fins 45 extending angularly on either side of the tooth 44, at the axial end of the latter facing the rotor 5.

[0061] In this figure 4, the flow lines F crossing the cylinder head 4 are shown in black lines. It can be seen that the radial groove 42 is not or very little crossed by the flow lines F, due to its central position at the base of the tooth 44.

[0062] In an alternative embodiment of the invention, the radial grooves 42 do not intersect the ortho-radial plane of symmetry P, this condition being difficult to achieve when the stator is made by winding a sheet metal (so-called "slinky" method in English). In this case, the radial grooves 42 are nevertheless equidistant from each other in the angular direction, this condition however not being necessary to achieve the invention. Each groove 42 is viable provided that the shortest distance d1 (referenced figure 4) between the groove and the adjacent winding notch is substantially equal to or greater than the thickness d2 of the yoke.

[0063] Returning to Figure 1, the electrical connection 34 connects the phase connection 74 to the phase terminal 94 without angular deviation, these three elements being centered on the ortho-radial plane of symmetry P of the same stator tooth 44.

[0064] On a first side of this ortho-radial plane of symmetry P, the electrical connection 36 connects the phase connection 76 to the phase terminal 96 by passing through a radial groove 42 located in a stator tooth 44 spaced by only one other stator tooth 44 from the stator tooth 44 through which the electrical connection 34 passes.

[0065] Symmetrically, on a second side of the ortho-radial plane of symmetry P, distinct from the first side mentioned above, the electrical connection 32 connects the phase connection 72 to the phase terminal 92 by passing through a radial groove 42 located in a stator tooth 44 spaced by only one other stator tooth 44 from the stator tooth 44 through which the electrical connection 34 passes.

[0066] Leaving, in the angular direction, at least one radial groove 42 out of two free of any electrical connection, makes it possible to use these free radial grooves 42 for the correct positioning of segments of the cylinder head 4 on the flat wall 20 of the casing. This also makes it possible to guarantee the feasibility of the path of the electrical connections 32, 34, 36 in terms of radii of curvature.

[0067] The phase connections 72 and 76 are located in the extension of the radial grooves 42 receiving the electrical connections 32 and 36, these therefore not having any angular deviation between the phase connections 72, 76 and the external radial periphery 48 of the yoke 4. The electrical connections 32 and 36 have, on the other hand, beyond the external radial periphery 48 of the yoke 4, several bends to reach the respective phase terminals 92 and 96.

[0068] As shown in Figure 2, the electrical connections 32, 34 and 36 of each stator 3 join two by two at their ends electrically connected to the phase terminals 92, 94, and 96. Thus the electrical machine 1 has a single terminal per phase for the two stators 3, accessible via a cover 24 on the radial extension of the cylindrical wall of the casing 2_2. Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the characteristics of different variant embodiments can be combined to implement the invention, insofar as these variants are not incompatible with each other.

Claims

CLAIMS 1- Axial flux electric machine (1), comprising: - a rotor (5), - a stator (3) comprising a yoke (4), teeth (44) projecting from the yoke (4) towards the rotor (5), and stator windings (8) wound around the teeth (44), the yoke (4) having a crown shape extending radially from an inner radial periphery (46) of the yoke (4) to an outer radial periphery (48) of the yoke (4), - a casing (2_1, 2_2) housing the stator (3), the cylinder head (4) being secured to a wall (20) of the casing (2_1, 2_2), - a circular bus (7) to which ends (80) of the stator windings (8) are connected, the circular bus (7) being arranged radially on the side of the inner radial periphery (46) of the yoke (4), the electric machine (1) being characterized in that the yoke (4) comprises on the side of the casing (2_1, 2_2), passages (42) passing radially through the yoke (4) and extending from the inner radial periphery (46) of the yoke (4) to the outer radial periphery (48) of the yoke (4), and in that the electric machine (1) further comprises electrical connections (32, 34, 36) capable of electrically connecting phase connections (72, 74, 76) of the circular bus (7) to phase terminals (94, 96) located in an outer peripheral portion (9) of the electric machine (1), the electrical connections (32, 34, 36) passing at least partly through the passages (42) radially passing through the cylinder head (4). 2- Axial flux electrical machine (1) according to claim 1, in which the electrical connections (32, 34, 36) are covered with an electrically insulating material at least on portions thereof in the passages (42) radially passing through the yoke (4). 3- Axial flux electrical machine (1) according to claim 1 or 2, in which the electrical connections (32, 34, 36) each connect a phase connection (72, 74, 76) distinct from the circular bus (7) to a distinct phase terminal (92, 94, 96) located in the external peripheral portion (9) of the electrical machine (1), passing through distinct passages (42) radially crossing the yoke (4). 4- Axial flux electric machine (1) according to any one of claims 1 to 3, in which the passages (42) radially passing through the yoke (4) each have a plane of ortho-radial symmetry common with a tooth (44) of the stator (3) or each have an ortho-radial symmetry plane located angularly at the level of a tooth (44) of the stator (3), the distance between the passage (42) and a winding notch adjacent to the tooth (44) being greater than or equal to a thickness of the yoke (4). 5- Electrical machine (1) with axial flux according to claims 3 and 4, in which one of the phase terminals (94) and one of the phase connections (74) of the circular bus (7) intersect the plane (P) of ortho-radial symmetry, one of the electrical connections (34) connecting said phase terminal (94) to said phase connection (74) following the plane (P) of ortho-radial symmetry. 6- Axial flux electric machine (1) according to any one of claims 1 to 5, in which the passages (42) radially passing through the yoke (4) are radial grooves formed on a surface of the yoke (4) opposite the wall (20) of the casing (2_1, 2_2). 7- Axial flux electrical machine (1) according to claims 4 to 6, in which the yoke (4) comprises a radial groove (42) per tooth (44) of the stator, the electrical connections (32, 34, 36) leaving a radial groove (42) free between them, the phase terminals (92, 94, 96) being grouped at an external periphery of the same tooth (44). 8- Electrical machine (1) with axial flux according to any one of claims 1 to 7, in which the circular bus (7) comprises one conductive bar per phase, the conductive bars being connected to the ends (80) of the stator windings (8) by forks (78) arranged angularly on these conductive bars, all of the conductive bars being overmolded while leaving free the phase connections (72, 74, 76) connected to the electrical links (32, 34, 36). 9- Electrical machine (1) with axial flux according to any one of claims 1 to 8, comprising two stators (3) and two corresponding circular buses (7), the electrical connections (32, 34, 36) of each stator (3) being electrically connected to each other in a terminal block comprising said phase terminals (92, 94, 96), in the external peripheral portion (9) of the electrical machine (1), located in a radial extension of the casing (2_1, 2_2) of the electrical machine (1). 10- Electric or hybrid electric vehicle, comprising an electric machine (1) according to any one of claims 1 to 9.

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